This is a contribution to the Proceedings of the 2007 Midwest Geometry Conference in honor of Thomas P. Branson, published in SIGMA (Symmetry, Integrability and Geometry: Methods and Applications) at http://www.emis.de/journals/SIGMA/
The $(2k)$-th Gauss-Bonnet curvature is a generalization to higher dimensions of the $(2k)$-dimensional Gauss-Bonnet integrand, it coincides with the usual scalar curvature for $k=1$. The Gauss-Bonnet curvatures are used in theoretical physics to describe gravity in higher dimensional space times where they are known as the Lagrangian of Lovelock gravity, Gauss-Bonnet Gravity and Lanczos gravity. In this paper we present various aspects of these curvature invariants and review their variational properties. In particular, we discuss natural generalizations of the Yamabe problem, Einstein metrics and minimal submanifolds.
In this paper, we prove the extensions of Bonnet--Myers' type theorems obtained by Calabi and Cheeger--Gromov--Taylor via Bakry--Emery Ricci curvature, which generalize the results of \cite{FG, Lim1, Wan, Wang, WW, Wu}.
We introduce the notion of Bonnet-Myers and Lichnerowicz sharpness in the Ollivier Ricci curvature sense. Our main result is a classification of all self-centered Bonnet-Myers sharp graphs (hypercubes, cocktail party graphs, even-dimensional demi-cubes, Johnson graphs $J(2n,n)$, the Gosset graph and suitable Cartesian products). We also present a purely combinatorial reformulation of this result. We show that Bonnet-Myers sharpness implies Lichnerowicz sharpness. We also relate Bonnet-Myers sharpness to an upper bound of Bakry-Émery $\infty$-curvature, which motivates a generalconjecture about…
The Yamabe problem for Gauss-Bonnet curvatures: a local result around space forms
在M. L. Labbi等人证明了在n维闭流形1<2k<n上具有常数2k-Gauss-Bonnet曲率的度量是Hilbert型泛函关于保体积共形变分的临界点.这就引出了相应的Yamabe问题：在一个闭流形上的任何度量是否共形于一个具有常数2k-Gauss-Bonnet曲率的度量？对于某些空间型的小扰动，我们用微扰方法肯定地回答了这个问题。更精确地说，如果（X，g）是一个非平坦的闭空间型，与一个圆球不等距，我们证明了g在度量空间中存在一个邻域U，使得U中的任何g'共形于一个其2k-Gauss-Bonnet曲率为常数的度量.
This paper defines two new extrinsic curvature quantities on the corner of a four-dimensional Riemannian manifold with corner. One of these is a pointwise conformal invariant, and the conformal transformation of the other is governed by a new linear second-order pointwise conformally invariant partial differential operator. The Gauss-Bonnet theorem is then stated in terms of these quantities.
We give an explicit formula for the Gauss-Bonnet-Chern mass of an asymptotically flat graphical manifold of arbitrary codimension and use it to prove the positive mass theorem and the Penrose inequality for graphs with flat normal bundle.
The Gauss-Bonnet-Grotemeyer Theorem in spaces of constant curvature
在1963年，K. P. Grotemeyer证明了高斯-博内定理的一个有趣的变体。设M是欧几里得空间R^3中具有欧拉示性数χ（M）、高斯曲率G和单位法向量场n的定向闭曲面。格罗特迈耶恒等式用法向矩<a，n>^2G代替高斯-博内被积函数G，其中$a$是固定的单位向量。Grotemeyer证明了这个被积函数的总积分是（2/3）pi乘以chi（M）。本文将Grotemeyer的结果推广到n维空间型N^{n+1}（k）中的n维定向闭偶维超曲面.
We study the Bonnet problem for surfaces in 4-dimensional space forms, where two isometric surfaces have the same mean curvature if there exists a parallel vector bundle isometry between their normal bundles that preserves the mean curvature vector fields. We deal with the moduli space of congruence classes of isometric surfaces with the same mean curvature, and with properties inherited on a surface by its structure. The study of this problem led us to a new conformally invariant property, called isotropic isothermicity, that coincides with the usual concept of isothermicity for surfaces lyin…
An equivalent definition of entropic Ricci curvature on discrete spaces was given in terms of the global gradient estimate. With a particular choice of the density function $ρ$, we obtain a localized gradient estimate, which in turns allow us to derive a Bonnet-Myers type diameter bound for graphs with positive entropic Ricci curvature. However, the case of the hypercubes indicates that the bound may be not optimal (where $θ$ is chosen to be logarithmic mean by default). If $θ$ is arithmetic mean, the Bakry-Émery criterion can be recovered and the diameter bound is optimal as it can be attaine…
The authors Balogh-Tyson-Vecchi in arXiv:1604.00180 utilize the Riemannian approximations scheme $(\mathbb H^1,<,>_L)$, in the Heisenberg group, introduced by Gromov, to calculate the limits of Gaussian and normal curvatures defined on surfaces of $\mathbb H^1$ when $L\rightarrow\infty$. They show that these limits exist (unlike the limit of Riemannian surface area form or length form), and they obtain Gauss-Bonnet theorem in $\mathbb H^1$ as limit of Gauss-Bonnet theorems in $(\mathbb H^1,<,>_L)$ when $L$ goes to infinity. This construction was extended by Wang-Wei in arXiv:1912.00302 to the …
Gauss-Bonnet theorem in sub-Riemannian Heisenberg space $H^1$
在亚黎曼海森堡空间$H^1$中证明了Gauss-Bonnet定理的一个版本。次黎曼距离使$H^1$成为度量空间，并与球面Hausdorff测度相合.利用这个测度，我们在曲面S的点处定义了一个高斯曲率，其中次黎曼分布横截于S的切空间。如果S的所有点都有这个性质，我们证明了一个Gauss-Bonnet公式，并为紧曲面（这是拓扑环面），我们得到$\int_S K = 0$。
The aim of this note is to provide an intrinsic proof of the Gauss--Bonnet theorem without invoking triangulations, which is achieved by exploiting complex structures.
